1. Field of the Invention
The present invention relates to a reference vibrator that is mounted to an unbalance measurement device for a rotary product and applies vibrations for repeatability check to the unbalance measurement device.
2. Description of the Related Art
In this application, the term “rotary product” means a device, such as a supercharger, that has a rotor inside.
For example, in manufacture of a high-speed rotary machine such as a supercharger, for inspecting and correcting balance performance of the rotary product at the time of high-speed rotation, a high-speed rotation balance test is conducted to measure an unbalance amount and perform unbalance correction. An unbalance measurement device is used for the measurement of the unbalance amount.
FIG. 1 shows a configuration of an unbalance measurement device 30 disclosed in a Patent Document 1 given below. This unbalance measurement device 30 is configured as a measurement device for a supercharger 41. The unbalance measurement device 30 includes: a vibration table 35 in which a plurality of spring elements 33 (for example, round rods) are secured to a top surface of a base 32 fixed on a floor surface 31, and an upper plate 34 is fixed and supported on the top of the spring elements 33; a turbine casing (product mount) 37 fixed on the vibration table 35 by a bolt 44 via a turbine casing mounting plate 36; an acceleration sensor 38 attached to the turbine casing mounting plate 36; a rotation detector 39 placed near a tip of a compressor impeller 42 of the supercharger 41; and a calculator 40 that calculates an unbalance amount and its position on the basis of detection signals from the acceleration sensor 38 and the rotation detector 39.
In the case of performing unbalance measurement by the above-mentioned unbalance measurement device 30, the rotary product (such as the supercharger 41) is mounted to the turbine casing 37, and air is introduced into the turbine casing 37 to rotate a turbine impeller 43 of the supercharger 41, thereby rotating a supercharger rotor composed of the turbine impeller 43, a shaft 45, and the compressor impeller 42. When a predetermined rotation speed for the unbalance measurement is reached, acceleration (vibration) is detected by the acceleration sensor 38, and also a rotation angle is detected by the rotation detector 39. An unbalance amount and its position are calculated by the calculator 40 on the basis of detection signals of the detected acceleration and rotation angle.    [Patent Document 1]    Japanese Patent Application Laid-Open No. 2002-39904
To stably detect the unbalance amount of the rotary product with constant accuracy, the unbalance measurement device needs to be calibrated not only at the time of manufacture but also at an appropriate timing after the manufacture. For instance, there is a need to replace the product mount (the turbine casing 37 in FIG. 1) according to the type of product that is subject to the unbalance measurement. Repeatability can be affected depending on, for example, the extent of tightening of the mount fixing bolt (the bolt 44 in FIG. 1) upon this replacement. Therefore, it is necessary to check and calibrate the repeatability of the unbalance measurement device.
Conventionally, when checking and calibrating the repeatability of the unbalance measurement device, for example a rotary product with excellent vibration properties is mounted to the mount as a reference rotor, and the reference rotor is rotated. However, repeatability of a vibration force of the reference rotor is poor, due to factors such as changes or variations in vibration state caused by environmental conditions and degradation of the reference rotor. This makes it impossible to judge whether the repeatability of the vibration force of the reference rotor is poor or the repeatability of the measurement device is poor, and so there is a problem of difficulty in properly checking the repeatability of the unbalance measurement device.